Disposal of municipal sewage and agricultural waste is often a costly process. Sewage and biological wastes, such as manure, are often disposed of by anaerobic microbial digestion to convert the digestible solid and liquid matter to a biogas composed primarily of CH4 and CO2. The biogas is often burned to avoid releasing the powerful greenhouse gas methane. Sometimes the heat from burning the biogas is used, for instance, to heat buildings or to power turbines and produce electricity. But heat and electricity are low-value products, so usually the disposal process remains a net economic drain.
In addition to failing to produce a high-value product, anaerobic digestion of sewage and biological wastes is frequently slower and more incomplete than would be desired. Anaerobic microbial digestion also produces hydrogen sulfide and other sulfhydryl compounds that corrode metal pipes and fermentation tanks and cause odors that are objectionable to neighbors of the waste-treatment plant.
New methods of disposing of sewage and other biological or organic wastes are needed. Preferably the methods would allow a more complete and efficient conversion of the wastes. Preferably the methods would remove or convert odor-causing compounds. Preferably the methods would produce a higher value product than current methods.